This invention relates to a fume extractor for a barrel of a gun, and to a barrel and a gun provided with such a fume extractor.
A known fume extractor (such as the one disclosed in U.S. Pat. No. 5,404,789) for extracting fumes from the bore of a barrel of a gun, after a shot has been fired, comprises a main reservoir and an auxiliary reservoir, both surrounding the barrel, with the auxiliary reservoir located between said main reservoir and the breech end of the tube. A first set of ports, which are slanted towards the muzzle end of the bore, provides communication between the main reservoir and the bore while a second set of ports, which are perpendicular to the bore, provides communication between the bore and the auxiliary reservoir. A set of check valves provides communication between the auxiliary reservoir and the main reservoir, when the pressure in the main reservoir is less than that of the auxiliary reservoir.
In use, when a shot is fired, owing to the pressure difference between the bore and the reservoir, the main and auxiliary reservoirs are charged or pressurised by fumes passing through the two sets of ports from the bore into the main and auxiliary reservoirs. The main reservoir is thus pressurised via the said first set of ports, as well as from the auxiliary reservoir via the set of check valves.
When the projectile leaves the barrel, there is a pressure drop in the bore, so the set of check valves closes and the pressure in the main reservoir is released by blowing the fumes back into the bore via the first set of ports in the direction of the muzzle brake, thus to extract the fumes from the bore.
A first disadvantage is that, owing to the fact that the known fume extractor has only two reservoirs; the resultant extraction is a rapid discharge rather than an extended discharge. In the case of a rapid discharge, the fumes are insufficiently extracted, leading to fumes entering the turret of the gun to the detriment of the operators thereof.
Another disadvantage of the known fume extractor is that it is of insufficient capacity to sufficiently cool down the fumes before reaching the check valves when the reservoirs are charged. The result is that the check valves are damaged by the high temperature and the acceleration or deceleration of the fumes. The check valves therefore eventually disintegrate and deform.
Yet another disadvantage of the known fume extractors is that the attachment thereof to the barrel, makes it very difficult to remove the fume extractor from the barrel for maintenance purposes, for example when the check valves have to be replaced.